1. Field of the invention
The invention relates to a device for monitoring the state of an electric switch having an open state and a closed state in which the closed state has an impedance less, by several orders of magnitude, than its impedance in the open state. It is suitable for use in all installations in a severe environment where monitoring of the control system of the switch is insufficiently reliable, since the state of the switch may not reflect that of the control system. The invention also relates to relays provided with such a monitoring devide and, in particular, solid state relays which have a history of being subject to breakdowns due to short circuiting of the solid state switch components which makes monitoring of the control particularly unreliable.
2. Prior art
Conventional electromechanical relays, while they are safe, have on the other hand numerous drawbacks, among which a large response time which limits the switching frequency, bouncing, sensitivity to a vibration environment, and wear of the contacts. Solid state relays have the advantage of a much shorter response time which allows switching rates beyond 10 kHz and currents comparable to those in electromagnetic relays when they use recently developed semiconductor components. But the risk of internal short circuits, which cannot be detected by monitoring the control, has led up to a now to reluctance to use solid state relays in a severe environment, particularly in launchers such as those used for launching satellites.